Sportfishers introduced the Zander, a type of perch, to Britain’s rivers and canals in the 1970s. Because zander eat large numbers of smaller fish, they have had a devastating effect on native fish populations. To protect the native fish, a government program removed a significant proportion of the zander from Britain’s waterways last year. Surprisingly, this year the loss of native fish to zander has been greater than before.

4. Which of the following, if true, would most help to explain the greater effect of zander on the native fish population?

A. The climate in Britain is very similar to the climate in regions to which zander are native.

B. Most of the zander removed were fully grown, and fully grown zander eat large numbers of smaller zander.

C. Every year a large number of zander are caught by sportfisher in Britain’s waterway.

D. Previous government program designed to remove nonnative species from Britain’s waterways have failed.

E. Zander are just one of several nonnative fish that prey on the other fish found in Britain’s waterway.

答案：B